1. Field of the Invention
The invention concerns personal care compositions providing moisturization both in high and low relative humidity environments.
2. The Related Art
Dry skin is a problem in varying degree to most humans. This condition is particularly evident in winter. Personal care products such as skin creams/lotions, shampoos/conditioners, toilette bars/shower gels and antiperspirant/deodorants are normally formulated with at least one material to adress dry skin. Symptoms such as itching, flaking and a visually displeasing dermal appearance can all to some extend be modulated.
There are three classes of materials employed against the problem. Occlusives such as petrolatum or silicone oils serve to inhibit loss of natural moisture. They form a barrier between the epidermis and the environment. Another approach is the use of keratolytic agents to enhance rate of dermal exfoliation. Alpha-hydroxy acids are the most common agents for achieving exfoliation.
A third approach to dry skin is topical application of humectants. Hydroxylated monomeric and polymeric organic substances are generally used for this purpose. Glycerin known also as glycerol is one of the most effective humectants.
There are several shortcomings in the performance of known humectants. Even the best such as glycerin requires to be formulated at relatively high levels to achieve good moisturization. Secondly, known humectants perform well in high relative humidity environments; however, hardly any of these substances provide effectiveness at low relative humidity (i.e. less than 20% moisture at 20° C.). Average indoor relative humidity during winter is approximately 13% in areas such as the Northeast U.S. It is quite evident that a real need exists for an improved moisturization technology.
A moisturizer known as Honeyquat 50 with INCI name of Hydroxypropyltrimonium Honey has been reported to be a better humectant than glycerin. See the Arch/Brooks brochure titled “Cosmetic Ingredients & Ideas®”, Issue No. 2, August 2001. Honeyquat 50 is described as being derived from the reaction of pendent hydroxyl groups (on the disaccharide) of a “light” deodorized grade of honey with a chlorohydroxytrimethylammonium derivative. Although this substance has excellent humectancy, moisturization at low relative humidity still remains to be conquered.
Accordingly, the present invention seeks to identify humectants which are operative not only at high but also low relative humidity, for application in personal care products.